"I am in the process of writing the next two Avatar films now. We are planning to shoot them together and post them together, and we will probably release them not quite back to back, but about a year apart. Christmas '14 and '15 is the current plan."
The news falls in line with a report from August which indicated Avatar 2 and Avatar 3 will be shot back-to-back. Without mentioning any names, James Cameron also said that any Avatar survivors will return for Avatar 2 and Avatar 3:
"Basically, if you survived the first film, you get to be in the second film, at least in some form."